1. Field of Invention
This invention relates to a chemical composition and a method for its use to extract gold, silver, and the platinum metals from precious-metal-containing ores.
2. Brief Statement of the Prior Art
Recovery of gold, silver, and the platinum metals from ores has traditionally been achieved by extraction with cyanides, by mercury amalgamation, flotation, and electrolytic separation and electrostatic separation. In the latter method, the metals in dry ore are electrostatically charged, usually passing a high velocity arc through the ore and then recovered on an oppositely charged collector. In electrolytic separation, the metals in an ore are dissolved and then electroplated on an oppositely charged electrode. Many other methods of separation include gravimetric differential density separation, chlorination, ion exchange, and other procedures both chemical and mechanical.
All of the aforementioned processes are costly, time consuming, and inefficient as they recover only a low fraction of the precious metals in the ore, or require the use of toxic chemicals which can be injurious to plant personnel, and damaging to plant and animal life when discharged to the environment.
Accordingly, there exists a need for a method which achieves greater recoveries of precious metals than currently practiced methods. There is further a need for a simple, low-cost, and efficient method for the extraction of gold, silver, and the platinum metals from precious-metal-containing ores without the use of toxic chemicals such as mercury, cyanides and strong acid leaches. A method is desired which is less costly in plant cost and labor than conventionally used mechanical procedures. Additionally a need exists for a process where precious metals can be obtained directly as free metals ready for refinery separation and in particular a process which poses no threat to the environment or ground water.